The invention relates to a tool for roughening a borehole surface, with a coupling portion for clamping the tool in a drilling machine and a tool head for machining the borehole surface, wherein circumferentially disposed cutting means are provided on the tool head.
For fastening building parts to foundations, it is known to fix profiled anchor bars by means of a chemical mortar compound in blind holes already drilled into the foundation. The blind holes can be drilled by means of diamond-surfaced tools. Depending on the material of the foundation, the borehole wall of such a borehole may be very smooth. In order to transfer even high tensile forces acting on the anchor bars reliably to the foundation, it is of advantage when the mortar compound in the cured condition interacts interlockingly with the borehole wall. This can be achieved by mechanically roughening at least part of the borehole wall or by providing it with profiling.
Tools and methods of the type mentioned in the introduction for roughening a borehole surface are therefore used in particular to increase the load-bearing capacity of chemical mortar compounds in diamond-drilled holes. In the process, the relatively smooth inner shell surface of a borehole is structured and, for example, provided with defined undercuts.
Various concepts are known for introducing such undercuts in a borehole surface. For example, DE 31 43 462 A1 and DE 38 19 650 A1 respectively describe tools on the tool shank of which a conical or cambered contact face is provided, to enable a user to superpose a wobbling motion manually on the tool rotation. In this way, the tool head is deflected in radial direction and penetrates into the borehole surface.
Furthermore, it is known from DE 103 34 150 A1 how to dispose a tool head eccentrically on a tool shank and in this way to achieve radial deflection of the cutters disposed circumferentially on the tool head.
DE 196 10 442 A1 proposes an asymmetric arrangement of tool cutters, so that the tool has an imbalance that generates a wobbling motion during drilling operation.
The already known solutions suffer from the disadvantage that both the operator and the drilling machine are greatly stressed by vibrations due to the wobbling motion of the tool. In addition, the result of the roughening process depends on the duration of application as well as on the machine guidance by the respective user. Furthermore, the cutting elements normally used for roughening, such as carbide or diamond cutting members, are exposed to severe wear, especially when they encounter rebar or hard rock during the roughening process.